| But as PCS data services are rolled out in the U.S., coverage will
become a critical issue. Competing digital technologies are available,
extensive roaming agreements still need to be hammered out, and far too
many so-called digital providers still rely heavily on analog cellular
in sparsely populated areas. Things will be better in Japan, Korea, and
many European countries, which have standardized on one digital technology
and have the dense population needed to justify the buildout of an all-digital
network.
Corporate networkers with sites in the San Francisco Bay area, Seattle,
Wash., or Washington D.C., also would do well to check out Ricochet, the
wireless IP offering from Metricom Inc. (Los Gatos, Calif.). At 28.8 kbit/s,
it outperforms any other wireless IP offering out there; its flat-rate
pricing also is attractive. The provider says it will expand into other
cities this year and indicates it's working on a 128-kbit/s network.
The Need for Speed
Faster wireless IP offerings are on the way. So-called 3G (third-generation)
cellular will deliver throughput as high as 2 Mbit/s in the local area
and 144 kbit/s for mobile. But the earliest these systems will arrive is
next year, and that's on a very limited basis. Most corporate networkers
who want wireless IP now are going to have to learn to live with 9.6 to
14.4 kbit/s-a big consideration given that even 56-kbit/s transfers can
seem agonizingly slow on today's Internet.
They're also going to have to deal with something else: latency-and
its potentially crippling effect on client-server applications.
Consider an SQL (structured query language) database or groupware/e-mail
apps like Exchange from Microsoft Corp. (Redmond, Wash.) and Notes from
Lotus Development Corp. (Cambridge, Mass.). These send a large number of
messages back and forth in the course of executing transactions. A single
query, for instance, could generate dozens of messages. With latencies
(and round-trip times) ranging from 0.5 to more than 5 seconds, a new screen
of information that takes a few seconds to update over a LAN could take
a half a minute or more over a wireless IP link .
Even this wouldn't be a complete disaster. But many end-users, after
staring at their screens for what feels like forever, assume the application
or machine has hung and terminate it. Or they reboot their PCs.
Then there's the problem of intermittent connections. These are not
uncommon with wireless services, particularly if the end-user is mobile.
(It's not much different from having a cellphone call dropped in the middle
of a conversation.) Some applications can shrug this off; others may become
unstable or damage data.
Set Up to Shut Up
So what can net managers do? For starters, find out how to configure
chatty applications so they only communicate essential information over
the wireless link. For example, by minimizing the amount of upfront synchronization,
it's possible to reduce a remote Microsoft Exchange login from over five
minutes to about one minute. Similarly, Lotus Notes can be configured to
replicate just the subset of the databases that end-users need to work
with, rather than all of them.
Another timesaver is to set up e-mail applications so they screen out
attachments or don't automatically download messages above a certain size.
Database apps also can be programmed to load data dictionaries from a local
cache rather than over the airlink. And even Web browsers can be set to
operate in text-only mode.
The Middleware Muddle
In some cases, the foregoing fixes may be sufficient. Even if they're
not, they'll get net architects thinking in the right direction. But if
applications are still plagued with problems, it's probably time to turn
to wireless middleware.
The benefits are real: Wireless middleware reduces both the amount of
information communicated over the air and the number of messages needed
to complete transactions. In many cases, it can actually queue messages
when end-users are outside of a coverage area. Further, it may use transport
protocols that are not only more efficient than TCP over airlinks but also
more resilient to wireless idiosyncrasies, like variable delay, that can
confuse TCP timing algorithms.
However, the downsides to wireless middleware are equally real. It adds
cost and complexity.
Wireless middleware is based on an architecture comprising software
loaded on the mobile computer (the middleware client) and software that
runs on a server (the mobile server), which acts as a proxy to access information
from other services on behalf of the mobile client using standard LAN and
WAN protocols (see Figure 1). The middleware client and server components
use special protocols to communicate with each other over the wireless
network.
The challenge is marrying the application to both the client and server
portions of the middleware. There are two basic approaches, and the difference
between them is huge.
In the traditional scheme, the middleware is supplied by the vendor
in a software developer kit (SDK) with APIs (application programming interfaces)
for the mobile client and server. It's up to the network manager and IS
staff to reengineer existing applications or develop new ones from the
ground up. This involves a substantial development effort. It also assumes
that corporate networkers already have or will develop the source code
for their apps-clearly not an option if they plan on using off-the-shelf
packages. (No wonder that wireless networking has chiefly been used in
vertical markets.)
To the Rescue
Fortunately, a new type of wireless middleware has recently emerged.
Like its SDK-based counterpart, it comes with client and server components.
But it requires almost no programming, other than simple setup; once that's
done, it automatically intercepts application and networking calls and
optimizes communications. Unfortunately, there are only a few products
out there now. The selection should improve, however, as wireless data
starts to enter the mainstream.
Smart IP from Nettech Systems Inc. (Princeton, N.J.) optimizes IP-based
communications, potentially making any IP application operate more efficiently
over wireless links. It also enables these apps to operate over packet-data
networks like Bellsouth Wireless and Ardis.
Laplink Enterprise from Traveling Software Inc. (Bothell, Wash.) is
another product to watch. The package includes an accelerator for Microsoft
Exchange that not only speeds up mail downloads but also gives end-users
far more control over what is downloaded and how. The vendor doesn't have
an accelerator available for Lotus Notes, however.
Whither Wireless?
There are a couple of other developments to watch in wireless middleware.
For instance, a number of large wireless providers have banded together
as the Wireless Application Protocol (WAP) Forum. The group is developing
standards that make Web content readily available to mobile wireless devices
like smartphones. AT&T's Pocketnet is a precursor to this equipment;
it melds a cellphone capability with a CDPD modem and a small-display browser.
Users interact with specially prepared content hosted on Web servers, communicating
via a gateway operated by AT&T.
The other development is the growing number of wireless service bureaus,
like Goamerica Communications Corp. (Hackensack, N.J.; www.goamerica.com)
and Wireless Knowledge LLC (San Diego; www.wirelessknowledge.com) the recent
joint venture between Microsoft and Qualcomm Inc. (San Diego). These offer
a variety of services, including hosting middleware.
Here's how it works. Rather than linking directly to the corporate intranet,
mobile workers establish connections to the service bureau, which has secure,
high-speed connection to the company intranet. The bureau accesses the
requested information and then presents it in a manner optimized for wireless
communication, employing formats like WAP or XML (extensible markup language).
Getting Grounded
Wireless IP may conjure up visions of packets streaming through the
air, but how that data reaches its destination on the landline network
is a critical concern. For most corporate networkers, this will be familiar
turf; the issues are common to remote access in general.
Wireless networks link to the rest of the world in three basic ways:
over private connections, over the Internet, and over the PSTN (public
switched telephone network). Private connections are the preferred approach
for Ardis and Bellsouth Wireless, customers using X.25 over leased lines.
Large CDPD customers, in contrast, use IP over frame relay PVCs (permanent
virtual circuits) to connect to the carrier.
Increasingly, though, wireless IP providers advocate the Internet as
the preferred connection method. With CDPD, as well as all future packet
services for PCS, the wireless network has a seamless link to the 'Net.
It's much easier for the carrier to point customers to this connection
than to deal with individual private connections.
Be aware that going with the Internet means that remote users on a wireless
IP network will have the same problems getting through the firewall as
dial-up users coming in through an ISP. Fortunately, VPNs (virtual private
networks) can deliver the requisite security, and an increasing number
of vendors are selling solutions. But not all the security standards, including
IPsec itself, are complete. And while many companies are evaluating VPNs,
most do not yet allow Internet-based remote access.
The third avenue of access, the switched public network, is the least
problematic for companies, since they already have dial-up systems in place
for remote users. If calls come in over a circuit-switched data service
on a cellular network (via either an analog or a digital link), they will
be switched into the PSTN and appear identical to other modem connections.
Many of today's cellular data services are, in fact, circuit-switched.
This will continue to be the case for the next few years, until wireless
packet-switched services start rolling out in earnest. Network architects
who start getting ready now are going to be in the right place to exploit
new services and technologies.
Peter Rysavy is president of Rysavy Research (Hood River, Ore.), a consulting
firm that helps companies research, develop, and deploy communications
technologies.
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